objtool: Don't make .altinstructions writable

When objtool creates the .altinstructions section, it sets the SHF_WRITE
flag to make the section writable -- unless the section had already been
previously created by the kernel.  The mismatch between kernel-created
and objtool-created section flags can cause failures with external
tooling (kpatch-build).  And the section doesn't need to be writable
anyway.

Make the section flags consistent with the kernel's.

Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls")
Reported-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/6c284ae89717889ea136f9f0064d914cd8329d31.1624462939.git.jpoimboe@redhat.com

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 523aa4157f801c82686f19a2cc9403a6ca6113bb..bc821056aba902e5630076f61273fdc5fb1c83cb 100644 (file)
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -684,7 +684,7 @@ static int elf_add_alternative(struct elf *elf,
        sec = find_section_by_name(elf, ".altinstructions");
        if (!sec) {
                sec = elf_create_section(elf, ".altinstructions",
-                                        SHF_WRITE, size, 0);
+                                        SHF_ALLOC, size, 0);
 
                if (!sec) {
                        WARN_ELF("elf_create_section");